An aging study is proposed to test the relationship between conscientiousness and the social environmental factors and health- related behaviors that contribute to health and longevity. There is accumulating evidence that conscientiousness plays a significant role in the health process through its effect on health behaviors, such as tobacco and alcohol consumption (Caspi, Begg, Dickson, Harrington, Langley, Moffitt, & Silva, 1997) and social environmental factors, such as divorce and social support (Tucker, Kressin, Spiro, & Ruscio, 1998; Tucker, Schwartz, Clark, & Friedman, 1999). Despite these initial links to health, the role of conscientiousness in the health process has not been systematically studied, nor have the effects of aging on the relation between conscientiousness and health been investigated. Preliminary data are reported which suggest that a comprehensive model of conscientiousness is linked to many of the health behaviors and social environmental factors that contribute to health and longevity . The proposed research has three aims to be tested in a representative sample of young, middle-aged, and older participants. The first aim is to use a multi-method, comprehensive assessment model of conscientiousness to predict the social environmental and health-behavior factors known to affect health. It is predicted that certain facets of conscientiousness, such as impulse control, will predict specific health behaviors, such as drug consumption, more precisely than other facets of conscientiousness. The second aim is to test how age affects the relationships among conscientiousness, health-related behaviors, and social environmental factors. It is predicted that the relationship between specific facets of conscientiousness and social environmental and health-behavior factors will diminish with age and that individuals who maintain consistently low levels of conscientiousness into middle and old age will show greater lifetime accumulation of behavioral risk factors that undermine longevity, such as more years of alcohol and tobacco use, fewer children, and fewer years of physical activity. The third aim is to establish the foundation for an ongoing longitudinal study of the relationship between conscientiousness and social environmental and health behavior factors that affect health across the life course.